A daily dose of exercise is good for both mind and body, but how much is enough?

To find out, researchers from the University of California, Irvine (UCI) examined more than 50 adults between the ages 50 to 85, half of whom had memory deficits and half of whom were mentally healthy. They divided the participants into two groups—one that exercised on a stationary bike for six minutes and another that did not. All provided a saliva sample, and to test their memory, were shown 20 images of animals and nature scenes. An hour after the exercise group worked out at 70% of their maximum ability, the volunteers were given a surprise memory test to recall as many images as they could from the previously viewed set.

Compared to the participants who did not exercise, all of the exercising participants, regardless of whether they had cognitive impairments or not, showed improved memory after their short spin on the bicycle. “We saw significantly better recall in the exercise group than in the non-exercise group,” says lead study author Sabrina Segal, in the UCI postdoctoral program. “This was particularly significant in cognitively impaired participants who almost doubled their recall improvement.”

The researchers, who published their results in the Journal of Alzheimer’s Disease, believe the benefit may be tied to an exercised-induced brain chemical called norepinephrine, which has a strong influence on memory. By examining the saliva samples, which the exercise group provided both before and after their exercise sessions, the researchers found that immediately following their workout, the exercise group had high levels of the enzyme salivary alpha amylase, a biomarker for norepinephrine. The link was even higher in participants who started out with cognitive deficits. Previous research with drugs that influence norepinephrine levels showed that increasing norepinephrine can improve memory, while blocking it impairs recall.

“What’s exciting to us about this is that not only did exercise increase the biomarker for this brain chemical, but we saw more of this chemical released and with that, better recall. This relationship has not been shown ever in context of exercise,” says Segal. “We have not tapped into this system yet, and it is a very powerful way of enhancing our memories.”

The relationship between exercise, norepinephrine and improved memories is still speculative, but the researchers plan to analyze other underlying biological factors that may be involved, as well as how long the memory benefits last. The work could provide a new way of treating or improving memory loss associated with both normal aging (those senior moments) as well as with dementia or neurodegenerative diseases like Alzheimer’s. Exercise, even short bouts of activity lasting as little as six minutes, may become a potent and relatively easy addition to drug- or behavior-based treatment strategies.

“The reason I am so excited is because we are looking at an older population. No one has looked at this relationship in cognitively impaired people. If we build on this study, we can look at the intensity of exercise as well as the duration and frequency to develop a more appropriate intervention to prevent people from becoming cognitively impaired and slow down the progression to Alzheimer’s disease in a healthy and natural way,” says Segal.